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Beth Stackpole
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Blogger
Leaky boat
Beth Stackpole   1/10/2012 6:41:37 AM
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What exactly is leaking into the river--oil, gasoline, what? Sounds like this could be one of those examples of designers caught up in the feature chase or redesigning for redesign sake without really considering the broader ramifications of their efforts.

 

Rob Spiegel
User Rank
Blogger
Re: Leaky boat
Rob Spiegel   1/10/2012 7:19:11 AM
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That's a good question, Beth. I suspect it's oil. If it's gasoline, boats might be blowing up in the water. I asked the author of this Monkey posting to weigh in. Hopefully we'll get the answer soon from the source.

Dave Palmer
User Rank
Platinum
Re: Leaky boat
Dave Palmer   1/10/2012 10:30:02 AM
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@Beth: If it's a hydraulic trim unit that's leaking, then I assume that what's leaking is hydraulic fluid.

Some dissimilar amorphous plastics can be ultrasonically welded, if they have similar chemical structures and if their melting points are within 50°F of one another.  But from the description, I'm guessing that at least one of the plastics is a glass-filled nylon, which is a semicrystalline plastic (not amorphous).

Moisture content can be a big problem in ultrasonic welding of nylon.  Nylons can absorb a significant amount of moisture from the atmosphere.  When the material is welded, the water turns into steam, which leads to a weak and porous weld.  This can be avoided by welding in the "dry" state immediately after molding, before the material has had an opportunity to absorb any moisture.

Glass content can also make ultrasonic welding more difficult.  Many ultrasonic welding equipment manufacturers won't recommend welding anything with more than 20% or 30% glass, although it is actually possible to do so.

Glancing briefly at Volvo-Penta user forums, it seems like many boat owners have encountered this problem.  The best solution I've come across seems to be to remove the welded plug, drill and tap the housing, and put in a metal plug.

LarryR46
User Rank
Iron
Re: Leaky boat
LarryR46   1/10/2012 11:53:17 AM
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Mercury outboard moved their PT hydraulic fluid (very much like auto xmission fluid) reservoir from inside the boat to outside the boat around 1980, depending on the model.  Since Volvo-Penta's original IO design was mostly high-jacked from Kiekhaefer in early 60s, it's fitting that Volvo should copy mercury marine's trim design albiet somewhat late.  The outside reservor is a much cleaner installation than the older external one with very many fewer connections and hyrdaulic fittings to leak.  Most of the leaks occur in the three actuating cylinders which would be outside the boat in either case.  I agree that leaking ATM is BAD for the environment and more effort should be put forth to eliminate leaks.  I'm not sure that keeping the reservoir inside the boat does this, however.  Making the replacement of seals in the actuating cylinders more straight-forward would also help.

williamlweaver
User Rank
Platinum
Re: Leaky boat
williamlweaver   1/10/2012 3:19:10 PM
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I hear you LarryR46. My parents purchased a new 1979 Aristocraft with a 170 hp Mercruiser I/O and we used it trouble-free through the 80's. What surprises me is that something that is so obvious to boat owners would not be easily detected/predicted or anticipated by design engineers. As is the case which Agile software development attempts to address with customers on the development team, I wonder how many of the Volvo engineers were actually boaters -- much like the problem of software designers that build user interfaces for bench-top laboratory instruments never having stepped foot in a chemical laboratory.

OLD_CURMUDGEON
User Rank
Platinum
Hydraulic Trimmers
OLD_CURMUDGEON   1/11/2012 12:34:40 PM
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The external placement of hydraulic trimmers for stern drives is not a new design.  Several manufacturers, including EVINRUDE & JOHNSON (same company ... OUTBOARD MARINE CORP.) placed the hydraulic pumps externally.  In the case of the outboard motors, this was done to eliminate the extra thru-the-hull piping necessary to implement the feature.  It was in the 1960s that engines were getting larger physically, & powerwise.  It became an impossible task to grab the cowling of the engine to tilt it upward.

Obviously, much of the design philosophy regarding outboard motors was also incorporated w/ sterndrives.  To compact the design, get the maximum utilization from the pump & minimize the piping, pumps were installed on the external bracketry of the I/O.  Other reasons for keeping things "tight" was to lessen the chance for these appendages to snag anything that might be in the water, or close to a dockage.

Finally, when the term hydraulic is used, it is implicit that it is in reference to hydraulic oil, and not gasoline.  Anyone reading this article would immediately understand that. 

TJ McDermott
User Rank
Blogger
Change the fluid?
TJ McDermott   1/12/2012 12:37:07 AM
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Why is oil necessary as the operating fluid?  Why not use a hydraulic fluid that will not pollute?  Like, water?  If the system leaks, a jug of distilled water can be used to fill the resevoir.  Or for drinking.

Just asking.

William K.
User Rank
Platinum
I/O drive hydraulics
William K.   1/12/2012 10:41:02 AM
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Water-based hydraulic systems usually require different materials, because corrosion is always a concern in hydraulic systems. You can get away with using just water if the system only has to function once. Rust can lock up almost any hydraulic system very thoroughly. What the problem sounds like is that no consideration was given to the possibility that the system might be serviced instead of being replaced. Some groups feel that change is always good, while others realize that possibly a change might be an improvement.

alschott
User Rank
Iron
Re: Leaky boat
alschott   1/20/2012 9:39:51 AM
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1 saves
@Dave,

You just gave us insight on a similar problem we were experiencing while molding in a nylon overmolded connector into an ABS cover.  Our mold house didn't take in account the temperature difference in melt temperatures between nylon and ABS. 

We resorted to backfilling the rear of the connector with epoxy to lock the connector in place and stop a leak path. 

Thanks,

Allen

BillG
User Rank
Iron
Re: Leaky boat
BillG   1/23/2012 12:02:34 PM
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Hello from Volvo Penta Engineering.  First, let me assure everyone that real people, not monkeys, designed the external style trim system complained about in this article.  We, too, were unsatisfied with the field experience and re-designed the system consistent with our ISO 9001 philosophy. 

To improve the trim system for our SX drives, Volvo Penta moved the entire system outside of the boat for several technical reasons:

·         The entire system can be assembled in a very clean hydraulic facility and shipped to the assembly plant filled with oil and tested. This was not possible with the old system.

·         There are one third fewer hydraulic connections to fail.

·         The entire pump and motor assembly are now in a sealed compartment – much more protected than it was in the back of the engine compartment.

With the original external system, the welding process of the plugs was a laser process, not an ultrasonic weld process, and the material content of plug and housing is the same except for color. This process was fully compatible with the materials being used; unfortunately there were manufacturing quality issues that were difficult to control which resulted in inconsistent welds. The hose connection to the pump and cylinders has not been a quality issue in the field.  The hose connection uses an O-ring for sealing and is a design currently used in automotive and medical applications with excellent reliability.   Nevertheless, a leaking plug is sometimes misdiagnosed as a leaking hose.

Two years ago Volvo Penta eliminated the plugs in the newer external design, effectively eliminating the plugs as a failure mode.  Replacement components for Volvo Penta trim system incorporate the newer design without plugs for improved performance and overall satisfaction for those older engines in the field. 

Please accept our sincere apologies for your disappointment with our external trim system design.  As you know, design is an evolutionary process and better designs arise from mistakes along the way.  We are confident in our newer external design trim system and think it matches the quality, durability and performance of your Stingray and the rest of your SX drive system.  We encourage you to go back to your Stingray and give it a try. 

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